Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology Feasibility and safety of exercise stress testing using an anti-gravity treadmill with Tc-99m tetrofosmin single-photon emission computed tomography (SPECT) myocardial perfusion imaging: A pilot non-randomized controlled study Patrick Daly, MD*, Regina Kayse, MD*, Steven Rudick, MD*, Nathan Robbins, MS*, Jennifer Scheler MD#, David Harris, MD*, Robert O’Donnell, MD*, Alok K Dwivedi PhD^, Myron C. Gerson, MD*. Division of Cardiovascular Health and Disease, Department of Internal Medicine, and Division of Nuclear Medicine*, Department of Radiology#, University of Cincinnati Medical Center, Cincinnati, Ohio , Division of Biostatistics & Epidemiology, Department of Biomedical Sciences^ ,Texas Tech University Health Sciences Center, El Paso, Texas Copyright American Society of Nuclear Cardiology

Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology BACKGROUND 1-Exercise is the AHA/ACC guideline-recommended stress modality for myocardial perfusion imaging, but many patients are unable to exercise to target heart rate on a conventional treadmill 2- .We examined the feasibility and safety of stress imaging using an anti-gravity treadmill in patients with perceived poor exercise capacity. Copyright American Society of Nuclear Cardiology

Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology METHODS Study type: Pilot non-randomized controlled study Study subjects: Included patients had an inability to exercise on the conventional treadmill due to a disabling comorbidity or less than moderate physical functioning; non-ambulatory patients were excluded. Study endpoints: Primary end point(s): Assess safety of anti-gravity exercise in patients undergoing cardiac stress testing Secondary end point(s): Compare myocardial image quality following anti-gravity stress and pharmacologic stress Study variables Table 1 Copyright American Society of Nuclear Cardiology

Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology RESULTS Variables Pharmacologic Anti-gravity p-value   Mean(SD) Age(years) 61.2(8.3) 59.3(9.1) 0.46 Height (inches) 67(4.1) 67.3(3.9) 0.81 Weight (pound) 210.8(43.8) 202.4(52.9) 0.56 Body mass index 32.9(5.8) 31.4(8.2) 0.49 Time on treadmill (seconds) ------ 455.2(169.5) Resting heart rate 74.4(11.9) 79.3(15.1) 0.22 Peak systolic BP 134.2(24.2) 164.3(23.7) 0.0001 Peak diastolic BP 73.9(11.2) 81.9(13.9) 0.0372 Rest systolic BP 144.7(19.8) 144.4(18.8) 0.97 Rest diastolic BP 76.9(10.4) 80.9(11.7) Peak heart rate 120.5(14) 134.9(17.9) 0.0042 Peak double product 16,296.1( 4010.77) 22,334.5(5,034.4) Pre-stress EF (%) 54.1(16.2) 55.4(12.7) 0.88 Pre-stress EDV (ml) 116.3(28.4) 117.6(63.1) 0.23 Pre-stress ESV (ml) 56.5(34.3) 57.9(56.1) 0.35 Post-stress EF (%) 55.5(14.6) 56.1(13.2) 0.93 Post-stress EDV (ml) 122.5(31.1) 115.2(60.8) 0.05 Post-stress ESV (ml) 57.8(36) 57(57.2) 0.29 N (%) Gender-female 11(55) 13(44.8) 0.57 Race-black 5(29.4) 17(58.6) 0.07 Indication 0.008 Coronary disease 1(5) 0(0) 0.41 Chest pain 7(35) 19(65.5) 0.046 Short of breath 9(45) 2(6.9) 0.004 Other 1.00 Pre-operative 2(10) 6(20.7) 0.45 Calcium blocker use 5(25) 0.74 Beta blocker use 6(30) 15(51.7) 0.15 Anti-anginal drugs held for 48 hours 11 (55) 27 (69) 0.25 Abnormal scan 8(27.6) 0.24 Table 1: Comparison of factors between control and test groups EF: ejection fraction; EDV: end diastolic volume; ESV: end systolic volume; BP: blood pressure; SD: standard deviation Copyright American Society of Nuclear Cardiology

Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology RESULTS Of the 49 study patients, 29 walked on the anti-gravity treadmill and 20 received regadenoson stress. Seventeen of the anti-gravity patients (59%, 95%CI: 39%-76%) reached target heart rate possibly obviating the need for pharmacologic stress. Mean exercise level on the anti-gravity treadmill was to Bruce stage 3 with duration 7 minutes and 36 seconds. Five of the anti-gravity test patients reached target with 25% unweighting and 12 with 50% unweighting. Only minor adverse effects were noted, limited to transient musculoskeletal discomfort in 5 patients who exercised on the anti-gravity treadmill. There was no significant difference (p=NS) in image quality between patients who exercised on the anti-gravity treadmill (4.30 ± SD 0.87) versus controls who received pharmacologic stress (4.28 ± SD 0.66). On multivariable analysis higher resting heart rate was the only predictor of achieving at least 85% of maximum predicted heart rate on the anti-gravity treadmill (odds ratio 1.16, 95% CI: 1.03- 1.31, p = 0.014). Copyright American Society of Nuclear Cardiology

Journal of Nuclear Cardiology | Official Journal of the American Society of Nuclear Cardiology CONCLUSIONS 1- Patients with self-perceived inability to walk effectively on a conventional treadmill, who are referred for diagnostic SPECT MPI, can safely exercise, often to target heart rate, on an anti-gravity treadmill. 2- Further study is indicated to directly compare the effectiveness of anti-gravity stress testing to exercise on a conventional treadmill as an adjunctive approach to stress MPI in patients with limited exercise capacity. Copyright American Society of Nuclear Cardiology